Bug 5156 - Generic interface methods cause AOT crash
Summary: Generic interface methods cause AOT crash
Status: RESOLVED NOT_ON_ROADMAP
Alias: None
Product: iOS
Classification: Xamarin
Component: XI runtime ()
Version: 5.2
Hardware: PC Mac OS
: --- normal
Target Milestone: Untriaged
Assignee: Zoltan Varga
URL:
Depends on:
Blocks:
 
Reported: 2012-05-17 18:45 UTC by Aaron Bockover
Modified: 2012-06-01 08:24 UTC (History)
2 users (show)

Tags:
Is this bug a regression?: ---
Last known good build:

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Status:
RESOLVED NOT_ON_ROADMAP

Description Aaron Bockover 2012-05-17 18:45:13 UTC
Just ran into another generic/AOT issue in MT. I feel like though this may be a little different than other virtual/generic/AOT issues.

Given an interface:

interface IGetter
{
    T Get<T>();
}

And an implementation:

class Getter : IGetter
{
    public T Get<T>() { return default(T); }
}

And some other class:

abstract class Session
{
    public abstract IGetter Getter { get; }
}

And an implementation thereof:

class IosSession : Session
{
    private IGetter getter = new Getter();
    public override IGetter Getter { get { return getter; } }
}

AOT will fail:

new IosSession().Getter.Get<ENUM_TYPE>();

However, if the interface is removed:

abstract class Session
{
    public abstract Getter Getter { get; }
}

And an implementation thereof:

class IosSession : Session
{
    private Getter getter = new Getter();
    public override Getter Getter { get { return getter; } }
}

Everything works.

I assume this is because the interface is essentially introducing virtual method dispatching and thus the crash "makes sense."

However I also feel like the compiler can determine that the only implementation of IGetter will be Getter throughout the lifetime of the program - the field IosSession.getter is assigned only once, and the override IosSession.Getter property will only return that field value.
Comment 1 Rolf Bjarne Kvinge [MSFT] 2012-06-01 07:19:32 UTC
Zoltan, this looks like one of the current AOT limitations, am I right?
Comment 2 Zoltan Varga 2012-06-01 07:39:22 UTC
Yes.
Comment 3 Rolf Bjarne Kvinge [MSFT] 2012-06-01 08:24:38 UTC
Closing as WONTFIX then.